The present invention relates generally to roofing and siding construction materials. More particularly, the present invention concerns a method of producing such construction materials from a mixture of plant fibers and portland cement.
There is an ever-increasing demand for construction materials having some or all of the following characteristics: relatively light weight, fireproof, waterproof, nailable, odorless, insulative and relatively inexpensive. In spite of the attractive properties of a dense building material consisting of plant fibers such as wood fibers bonded with portland cement, no such product has effectively been marketed. Only porous products consisting of excelsior bonded with portland cement or a magnesium oxychloride cement have seen limited use. It is difficult to bond portland cement to plant fibers because water-soluble compounds in the fibers inhibit the setting of the cement. Among these compounds are hemicelluloses, tannins, sugars and others. Heretofore, an effective agent for negating the adverse effects of these water-soluble compounds in the fibers has not been discovered.
Another problem is the effect of the motion of the fibers during the setting of the portland cement. Any springback of the fibers after being compressed or swelling and/or shrinking with absorption or desorption of water during the setting of the portland cement will fracture the tiny crystallities of cement as they slowly form. Since the strength of the cement depends on the intermeshing of these crystallites, their disruption will greatly weaken the cured product.
Heretofore efforts to control the adverse effects of these water-soluble inhibitors in a wood or other similar fiber composite material utilizing portland cement as a binder, have resulted in five different approaches:
(1) extracting the inhibitors; PA0 (2) accelerating the rate of set of the portland cement; PA0 (3) increasing the strength of the composite material by the addition of resins; PA0 (4) coating the surfaces of the fiber particles with materials compatible with cement (mineralization); and PA0 (5) changing the composition of the portland cement to obtain a material less sensitive to the inhibiting action of the water-soluble compounds. PA0 low cost composite building materials particularly adapted for exterior use; PA0 composite building materials made from plant fibers bonded with portland cement having the following properties: PA0 a process for manufacturing building materials of the aforementioned type which does not produce ecologically harmful effluents; PA0 building materials made from a plant fiber/portland cement mixture in which the adverse cement set inhibiting effects of the water-soluble compounds in the fiber are effectively negated; PA0 a process of manufacturing building materials from the aforementioned mixture in which the time that portions of the mixture must be held under compression is reduced to a minimum; and PA0 a method of producing composite building materials from a mixture of plant fibers with portland cement in which a wide variety of plant fibers may be utilized.
To date, none of these approaches has been economically successful.